They are deceptively simple, but shelves pack an impressive storage punch. You can fit more on a single shelf than you can in a standard kitchen cabinet. It's a matter of geometry: Since most dishware is round, you lose valuable space in the corners of boxy cabinets. But with open shelving, you can stagger the stacks of plates and bowls, tucking them to fill gaps. And since there is no door to close, the plates and platters can hang past the edges of the shelf. For the same reasons, open shelves work well in bathrooms, too.
Attaching cabinets, shelves, and cubbies to the wall lets you keep valuable inches on the floor while soaking up space all the way to the ceiling. Building in storage lets you customize it to fit your space, too, which means less wasted space. You don't to have fancy cabinets custom-made (though those are nice); you can compile stock cabinetry into a unit that meets your specific needs.
Finding extra storage space in a room can be as straightforward as switching out one piece of furniture for another. Trade a chest of drawers for a night table. Choose a bed with drawers or cubbies underneath it rather than the standard frame. In the bathroom, forgo a pedestal sink in favor of a vanity with an undercounter cabinet, and hang a medicine cabinet on the wall in place of a flat mirror.
Other times, you need the instincts of a detective to seek out extra square inches. A flat wall, for example, works deceptively well for storage: You can break through the drywall surface to nestle shelves between the studs. Under a staircase, you'll find a triangle of space which you can use to build shelves or a cabinet, or which you can leave open for storage furniture and hooks.